Supplementation of protected oilseeds in dairy cattle rations to improve productivity and profitability of small-scale farms in the tropics

Reno Martha¹, Despal², Toto Toharmat² and Yuli Retnani²

¹ Graduate Program Nutrition and Feed Science, Department of Nutrition and Feed Technology, Faculty of Animal Science, IPB University, Bogor 16680, Indonesia
despal@apps.ipb.ac.id
² Department of Nutrition and Feed Technology, Faculty of Animal Science, IPB University, Bogor 16680, Indonesia

Abstract

Dairy farmers in Indonesia struggle to meet national milk demand due to inadequate feed quality and reliance on inconsistent agricultural by-products. Wet industrial by-products like tofu, tempeh and brewery residues are prone to spoilage and irregular supply. This study evaluated the effects of supplementing lactating dairy cow rations with durable, high-quality dry feeds, including roasted soybeans, jack beans and palm kernel meal (PKM), on livestock performance and farm profitability. Sixteen Holstein cows were fed control and supplemented rations for 56 days at a small-scale dairy farming area (KUNAK) in Cibungbulang, Bogor, Indonesia. The results revealed significant enhancements in dry matter intake (DMI), milk yield and profitability. PKM achieved the highest DMI (16.42 kg/day) and milk production (13.77 L/day), along with the best milk persistency (120.77%) and feed efficiency (0.85 kg DMI/kg Milk). Supplementation also enhanced milk composition, particularly solids-not-fat and protein content and improved feed efficiency. As a local feed substitute for imported soybean meal, PKM showed excellent nutrient utilization and profitability, making it a suitable choice for small-scale farmers. These results highlight the potential of local feed (PKM) and other oilseed/meal-based supplements to improve productivity and profitability in Indonesian dairy farming while addressing feed quality challenges.

Keywords: feed efficiency, jack bean, milk production, palm kenel meal, soybean

Introduction

In Indonesia, dairy farmers can only meet 22.7% of the national milk demand, with 80% of this supply coming from small and medium-scale farms producing between 10 and 15 liters of milk per day (BPS 2020). This limited milk production is primarily due to the poor nutritional quality of feed. Research by Despal et al (2019) highlights that improving feed quality can significantly enhance both milk production and milk quality. However, for smallholder farmers in Indonesia, feed quality is often inconsistent due to the use of natural grasses, agricultural and plantation residues and limited land availability. Farmers also heavily depend on industrial by-products such as tofu dregs, brewer's spent grain and cassava pulp (Anzhany et al 2022; Riestanti et al 2021). These industrial by-products are characterized by high moisture content and short shelf life, making it a persistent challenge to maintain feed quality.

Feeds derived from grains and oilseed meals offer a promising alternative to enhance the nutritional value of dairy cattle feed (Del Prado et al 2013). Feeds such as soybeans, jack beans and palm kernel meal are rich in protein and have the potential to improve milk production and quality. Additionally, the fats in these feeds can increase the energy density of the diet. However, careful consideration is needed when incorporating high-fat feeds, as excessive fat levels can disrupt rumen microbial activity. As the world’s largest producer of palm oil, Indonesia generates approximately 5 million tons of palm kernel meal annually (BPS 2023). Palm kernel meal can serve as a protein source, similar to the widely used imported soybean meal. Furthermore, jack beans, which can be cultivated in Indonesia, are being extensively studied as an alternative protein source to replace soybeans.

Proteins in feed are prone to degradation by rumen microbes, which can reduce their nutritional benefits (Zhang et al 2022). Research shows that a rumen-degraded protein (RDP) percentage of 60% can maximize microbial protein synthesis (Lima et al 2023). Feeds with high RDP content require protection to preserve their nutritional value (Putri et al 2021). Heat treatment is a proven method to protect proteins from degradation and stabilize fats (Rashid et al 2022). Techniques such as roasting at moderate heat for 20 minutes have proven effective in laboratory settings (Martha et al 2024). However, their application at the smallholder farm level remains underexplored. Excessive heat treatment may reduce protein digestibility and cause fat oxidation, leading to by-products such as free fatty acids and peroxides, which can lower overall feed quality. Moreover, technologies that can technically enhance nutrient utilization efficiency in the laboratory and improve livestock performance in the field need to be tested on farms, as farmers will only adopt technologies that provide both short-term and long-term profitability.

This study aims to compare the supplementation of roasted soybeans, jack beans and palm kernel meal in lactating dairy cow rations to improve livestock performance and farm profitability.

Materials and methods

Livestock and study conditions

The study was conducted in the Cibungbulang Small-Scale Dairy Farming Business Area (KUNAK) using open-stall cages. The average temperatures in the cages were recorded as 23°C in the morning, 28°C in the afternoon and 25°C in the evening, with relative humidity (RH) levels of 98%, 80% and 93%, respectively. The research lasted for 56 days, comprising a 49-day preliminary phase followed by a 7-day data collection phase.

Sixteen Holstein cows, with an average body weight of 480 kg and in the early to mid-lactation phase, were managed intensively following standard farmer practices. Rations were provided twice daily, in the morning and evening. Milking was conducted twice a day, at 06:00 and 15:30, with milk samples collected during both the morning and afternoon milking sessions.

Feeds and feeding

The feed used in this study consisted of elephant grass, concentrate, tofu dregs and roasted oilseeds/meals (soybeans, jack beans and palm kernel meal). The nutrient composition of the feed is shown in Table 1. The control ration (CTL) comprised 37.35% elephant grass, 20.04% concentrate and 42.61% tofu dregs. The average daily intake of the control ration was 12.77 kg of dry matter, equivalent to 3.17% of body weight.

The treatment group animals (SBM, JBM, PKM) were fed the control ration supplemented with protected oilseeds/meals, amounting to 20% of the control ration (w/w DM). The composition and nutrient content of the rations are presented in Table 2.

Preparation of protected oilseed supplements

Oilseeds and meals are protected through dry heating (roasting) manually at medium heat for 20 minutes. Once roasted, they are allowed to cool and then ground using a medium-speed grinder for 1–2 minutes. The protected oilseed/meal is subsequently mixed with concentrate before being fed to the livestock. The processing flowchart for the protected oilseed supplement is presented in Figure 1.

Figure 1. Process of preparing the protected oilseed supplement

Measurement of dry matter and nutrient consumption

The amount of ration provided during the collection period was recorded. Feed samples were weighed, dried, ground and analyzed in the laboratory for proximate composition, including dry matter, ash, crude protein, fat and crude fiber. Feed residues were also weighed daily for 7 days. Each day, 10% of the feed residues were composited, dried, ground and sent to the laboratory for proximate analysis. Dry matter and nutrient consumption were calculated by subtracting the amount of unconsumed residue from the total feed and nutrient intake.

Measurement of livestock performance

Livestock performance was evaluated based on the short-, medium- and long-term impacts of supplementation. The short-term impact was assessed through manure scoring, the medium-term impact through milk production and its components and the long-term impact through body condition scoring.

Manure and body condition scores were recorded on day 7 of the collection phase using the method described by Despal et al (2017). Milk production during the collection phase was measured volumetrically during morning and evening milking sessions. Milk samples of 250 ml each were collected and analyzed in the laboratory for composition, including solid non-fat, lactose, fat and protein content, using a lactoscan.

Feed-to-Milk Conversion Efficiency

Feed-to-milk conversion efficiency was assessed as an indicator of farm profitability, reflecting how effectively feed is converted into milk. This metric serves as a key measure of dietary efficiency and economic sustainability. It was calculated by comparing the average daily dry matter intake (DMI, kg) with the corresponding daily milk production (kg), as shown in the formula below:

Data collection and analysis

This study utilized a group randomized design with four replications. The cows were grouped based on their initial milk production levels. The treatments tested were CTL (control ration), SBM (control ration + 20% roasted soybean), JBM (control ration + 20% roasted jack bean) and PKM (control ration + 20% roasted palm kernel meal). Observed parameters included feed and nutrient intake, milk production and composition, manure score, body condition score and feed-to-milk conversion efficiency. Data were analyzed using ANOVA, with significant differences among treatments further examined using contrast orthogonal. Statistical analysis was performed using SPSS software version 25.

Statistical model

The statistical model used in this study is represented as follows:

Y _ij = μ + α_i+ β _j + € _ij

Where;

Y _ij : Observed value for the i-th treatment, j-th group

μ : Overall mean

α _i : Effect of the i-th treatment

β _j : Effect of the j-th group

€ _ij : Random error associated with the i-th treatment and j-th group

i : Treatment level (1, 2, 3 or 4)

j : Replication group (1,2,3 or 4)

Result and discussion

Impact Supplementation of Dry matter and nutrient intake

The dry matter and nutrient intake of cattle across treatments is summarized in Table 3. Supplementation significantly increased nutrient intake, except for ash and crude fiber, while dry matter intake (DMI) was significantly higher in the JBM and PKM groups compared to CTL and SBM. However, supplementation did not significantly affect intake per kilogram of body weight. Notably, PKM (palm kernel meal) resulted in the highest DMI (16.42 kg/day), driven by its lower energy density and higher fiber content, which stimulated greater consumption to meet energy and nutrient demands. This aligns with the concept of energy homeostasis, where animals consume more low-energy rations to fulfill nutritional needs.

Protein intake was highest in the SBM group (2.38 kg/day), supported by the high protein content of soybean meal. Protein is essential for milk synthesis and studies (e.g., Kim and Lee 2021) confirm the positive impact of high-quality protein supplementation on milk production. Although PKM provided lower protein intake (2.23 kg/day), it remained adequate to support production while offering cost-efficiency compared to imported protein sources. SBM also showed the highest fat intake (1.14 kg/day), attributable to the high fat content of soybean. Dietary fat enhances milk fat content (Bauman and Griinari 2003), critical for meeting market quality standards. PKM, with moderate fat content (1.02 kg/day), served as a cost-effective alternative without compromising production efficiency.

Crude fiber intake was highest in the PKM (3.49 kg/day) and JBM (3.09 kg/day) groups, essential for maintaining rumen health and fermentation. Fiber supports microbial activity, aiding digestion and energy metabolism (Ahmad et al 2020), while also slowing protein fermentation to improve utilization. Fiber levels in PKM ensured rumen function and prevented metabolic disorders like acidosis, aligning with recommendations of 17–22% crude fiber in dairy cow rations (Despal et al 2017). Crude fiber content decreased in SBM (18.64%) and JBM (20.15%) compared to CTL (22.14%), but remained consistent in PKM.

The total digestible nutrients (TDN) were highest in the SBM group (60.94%), emphasizing soybean meal's potential to meet energy demands for milk production. Palm kernel meal (PKM) also showed a respectable TDN value (57.34%), demonstrating its efficiency in supporting energy conversion for milk synthesis (Pan et al 2023). Despite lower crude protein and fat content, PKM supplementation improved feed efficiency and reduced feed costs, making it a practical alternative to high-cost imported ingredients like soybean meal (Connor 2015). Overall, this study highlights the benefits of oilseed/meal supplementation in enhancing nutrient intake and supporting productive performance in lactating dairy cows.

Impact supplementation on livestock performances

The impact of supplementation on animal performance is summarized in Table 4. Statistical analysis revealed that oilseed/meal supplementation significantly increased milk production compared to the control (CTL), with the highest increase observed in PKM (palm kernel meal). Both JBM (jack bean) and PKM treatments resulted in greater milk production than the initial levels, leading to milk persistency exceeding 100%. In contrast, although milk production in SBM (soybean) decreased slightly from the initial level, the decline was less pronounced than in CTL, where persistency was only 91%. Persistency in SBM reached 97.5%, while PKM achieved the highest persistency at 120.77%.

Supplementation significantly influenced the composition of milk. SBM resulted in the greatest increase in solids-not-fat (SNF) (+0.41) and protein content (+0.15%), reflecting an improved nutrient balance supporting milk component synthesis. Palm kernel meal (PKM) supplementation also improved protein content but led to a decrease in milk fat (-1.04%) compared to other treatments. This reduction in milk fat could be attributed to a decline in fibrolytic enzyme activity, acetate production (a precursor for fat synthesis) and lipogenic enzyme activity in the mammary gland (Palmquist and Jenkins 2017; Plata-Pérez et al 2022). Despite this, PKM supplementation enhanced total energy availability and had no adverse health effects. Low fat content in PKM milk might also caused by the increasing milk production. Negative correlation between milk production and milk fat content was also found by Despal et al (2021).

Lactose content increased across all supplemented groups, with the most notable rise observed in SBM (+0.23%), emphasizing the role of supplementation in enhancing glucose metabolism, which is critical for lactose synthesis. PKM supplementation further supported this process by promoting rumen fermentation and propionate production, a key glucose precursor for lactose synthesis (Mulliniks et al 2011). The positive correlation between lactose content and milk production is attributed to the role of lactose in regulating milk volume through osmotic balance, as water follows lactose into the mammary gland during milk synthesis (Antanaitis et al 2024). Additionally, concentrate supplementation has been widely associated with increased milk production and elevated lactose levels, further supporting the findings in this study.

Oilseed/meal supplementation enhanced energy availability while promoting fiber fermentation in the rumen, resulting in the production of volatile fatty acids (VFAs), a primary energy source for milk synthesis (Wilkinson and Young 2020). Its high crude fat content (7–12%) and bypass protein effectively met the metabolic demands of lactating cows, improving nutrient conversion efficiency (Dong et al 2023). Additionally, the bypass protein, produced using roasting techniques, successfully bypassed rumen degradation, increasing amino acid absorption in the intestine and directly supporting milk protein synthesis (Sinclair et al 2014). Unlike milk fat content, which tends to decline with increased milk production, milk protein content remained stable or even slightly increased in SBM, leading to greater overall milk protein output. These findings highlight the potential of oilseed/meal to sustain milk yield while enhancing milk quality and nutrient utilization efficiency.

Supplementation improved body condition scores (BCS) across all treatments, demonstrating its dual role in supporting milk production and maintaining energy reserves. Supplementation enhanced energy metabolism and supported recovery of body condition during high-energy lactation stages (Chanjula et al 2010). The highest milk persistency observed in PKM (120.77%) underscores PKM’s ability to sustain consistent milk production by supporting long-term energy metabolism. This aligns with findings by Dong et al (2023), who reported improved nutrient conversion efficiency with PKM supplementation.

Although the manure score was slightly lower in cows fed supplemented rations, the scores remained within the normal range for lactating cows. No cases of diarrhea were observed during this experiment, despite the high fat content in the oilseed/meal supplements. This indicates that oilseed/meal supplementation did not impair digestion, absorption, or rumen health.

Impact of supplementation on farm profitability

The impact of supplementation on farm profitability is presented in Table 5. The results show that oilseed/meal supplementation significantly enhanced farmer profitability by increasing milk production and feed-to-milk conversion efficiency. While supplementation raised ration intake compared to the control (CTL), the increase varied among treatments, with PKM (palm kernel meal) incurring the highest feed intake. However, this higher intake was offset by the substantial increase in milk yield, with PKM achieving the highest production at 13.77 L/cow/day compared to 8.22 L/cow/day in CTL. A gradual increase in milk production was also observed in SBM and JBM, demonstrating the effectiveness of supplementation in enhancing dairy cow productivity.

Oilseed/meal supplementation also significantly improved feed-to-milk conversion efficiency, with the largest increase observed in PKM (0.85), indicating its profitability despite higher feed intake. These findings align with Carvalho et al (2006), who noted that supplementation with protein- and energy-rich ingredients, such as PKM, balances the energy and protein needs of dairy cows, leading to increased milk production and profitability. This improvement reflects the cows' ability to utilize nutrients more effectively, producing more milk per kilogram of feed dry matter.

The profitability of supplementation is driven by increased milk production and optimized nutrient utilization. Andrade et al (2018) highlighted that PKM supplementation enhances rumen fermentation and energy use efficiency, leading to higher milk yields and improved economic returns. Furthermore, locally available feed resources such as PKM provide a cost-effective alternative to imported protein sources like soybean meal, further boosting profitability. The favorable fatty acid profile of PKM has also been shown to enhance digestibility and energy metabolism, supporting greater feed efficiency and overall productivity (Omotoso et al 2021; Umunna et al 1994).

Conclusion

This study demonstrated that supplementation with roasted soybeans, jack beans (JBM) and palm kernel meal (PKM) significantly enhanced dairy cow performance and farmer profitability. Among the treatments, PKM had the greatest impact, increasing dry matter intake and milk yield. Supplementation improved milk composition, particularly solids-non-fat and protein content, alongside better feed efficiency and nutrient utilization. PKM proved to be a cost-effective alternative to imported soybean meal, lowering feed costs without compromising performance. These results highlight PKM as an effective and practical strategy for boosting productivity in Indonesian dairy farming.

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